1. Field of the Invention
The present invention relates to a light emitting diode (LED) driving apparatus for directly driving an LED using alternating current (AC) power.
2. Description of the Related Art
A light emitting diode (LED) is a semiconductor element having a p-n junction structure and emitting light through electron-hole recombination, and has recently been used in various fields, according to the development of semiconductor technology.
Particularly, since an LED has high efficiency, a relatively long lifespan, and environmentally friendly characteristics, as compared to a light emitting device according to the related art, a range of applications thereof is continuously being widened.
Generally, an LED may be driven by applying several volts of direct current (DC) voltage thereto, due to a structure thereof. Therefore, in order to drive the LED using commercial alternating current (AC) power, commonly used domestically, commercially, or the like, a separate unit is required.
In order to drive the LED using commercial AC power, an LED driving apparatus typically includes a rectifying circuit, an alternating current-direct current converter (an AC-DC converter), and the like.
However, a general AC-DC converter has large volume and consumes a significant amount of power. Therefore, in a case in which a general AC-DC converter is applied to the LED driving apparatus, advantages of the LED such as high efficiency, a small packaging size, a long lifespan, and the like are largely canceled.
Therefore, research into an apparatus capable of directly driving an LED with AC power without using an AC-DC converter has been recently conducted.
In the case of directly driving the LED with AC power without using the AC-DC converter, a method in which a plurality of switches are respectively connected to a plurality of LEDs and switching on and switching off of the plurality of switches are controlled according to a level of the AC power to allow current to uniformly flow may be generally applied.
Patent Document 1 relates to an LED driving apparatus, in which an LED is directly driven to emit light using AC power by controlling operations of switches connected to a medium node and the last node of an LED array.
Patent Document 2 also relates to an LED driving apparatus, and discloses a configuration controlling switching on and switching off of a switch in an order in which LED arrays are connected.
However, while both Patent Documents 1 and 2 control the operation of the switch according to a level of the AC power, a waveform of input current due to switch driving is formed as a step-type waveform, thereby deteriorating a power factor and total harmonic distortion characteristics.